I hear my older coworkers use this idiom/phrase occasionally. It seems possibly to be a humorous way to get out of a conversation. Even as a native English speaker, I've never figured out the exact situation you would use this phrase. It almost sounds like it may have once been a punchline to a joke in a movie or something.

I'm curious what is the exact meaning/usage of this phrase/idiom? Where does it originate?

When i was a child, my grandfather use to excuse himself every morning by saying "I have to see a man about a dog". Much later, my grandmother explained to me that he was going to the bookies to bet on a horse race.
–
Kevin LawrenceJan 15 '11 at 7:29

2

The exact situation would be when you need to make arrangements about purchasing a dog from a man ;-)
–
SF.Nov 27 '12 at 16:06

4 Answers
4

The earliest confirmed publication is the 1866 Dion Boucicault play Flying Scud in which a character knowingly breezes past a difficult situation saying, "Excuse me Mr. Quail, I can't stop; I've got to see a man about a dog." In a listing for a 1939 revival on the NBC Radio program America's Lost Plays, Time magazine observed that the phrase is the play's "claim to fame".

This has been a useful (and usefully vague) excuse for absenting oneself from company for about 150 years, though the real reason for slipping away has not always been the same. [...] From other references at the time [around 1866] there were three possibilities: 1) [the speaker] needed to visit the loo [...] 2) he was in urgent need of a restorative drink, presumed alcoholic; or 3) he had a similarly urgent need to visit his mistress.

Of these reasons [...] the second became the most common sense during the Prohibition period. Now that society’s conventions have shifted to the point where none of these reasons need cause much remark, the utility of the phrase is greatly diminished and it is most often used in a facetious sense, if at all.

In my personal experience, this phrase and the horse variant were used specifically to excuse oneself to go to the restroom.
–
epotterNov 5 '10 at 17:15

What do you mean by "eliminates any lingering uncertainty about whether the hearer is being put off"?
–
PacerierJan 21 at 9:37

The phrase "see a man about a dog" is slightly ambiguous; it's conceivable that it might actually be true. By reversing the order, it makes it clear that the phrase isn't intended literally and is just a euphemistic way of saying "I'm not going to tell you why I'm leaving".
–
SnowbodyJun 1 at 18:48

"I have to see a man about a dog" is a thinly veiled semi-polite phrase which is used to excuse yourself from your current company, because you have to take a bog; where "take a bog" means to "take the time (out from the current situation) to defecate".

It may not be the original meaning, but then again, it may well be, because vulgar slang always pre-dates general public references to such phrases.

Well, that's my two cent's worth. But excuse me, I have to see a man about a dog...